21975749 has 4 divisors (see below), whose sum is σ = 21994860. Its totient is φ = 21956640.

The previous prime is 21975739. The next prime is 21975757. The reversal of 21975749 is 94757912.

It is a semiprime because it is the product of two primes.

It can be written as a sum of positive squares in 2 ways, for example, as 16662724 + 5313025 = 4082^2 + 2305^2 .

It is a cyclic number.

It is a de Polignac number, because none of the positive numbers 2^k-21975749 is a prime.

It is a super-2 number, since 2×21975749² = 965867088222002, which contains 22 as substring.

It is a Duffinian number.

It is a Curzon number.

It is a congruent number.

It is not an unprimeable number, because it can be changed into a prime (21975719) by changing a digit.

It is a pernicious number, because its binary representation contains a prime number (13) of ones.

It is a polite number, since it can be written in 3 ways as a sum of consecutive naturals, for example, 7712 + ... + 10169.

It is an arithmetic number, because the mean of its divisors is an integer number (5498715).

Almost surely, 2^21975749 is an apocalyptic number.

It is an amenable number.

21975749 is a deficient number, since it is larger than the sum of its proper divisors (19111).

21975749 is a wasteful number, since it uses less digits than its factorization.

21975749 is an odious number, because the sum of its binary digits is odd.

The sum of its prime factors is 19110.

The product of its digits is 158760, while the sum is 44.

The square root of 21975749 is about 4687.8298817257. The cubic root of 21975749 is about 280.1009372482.

The spelling of 21975749 in words is "twenty-one million, nine hundred seventy-five thousand, seven hundred forty-nine".